ELECTROLYTIC IRON
; DEPOSITED BY T H E COMMI T T E E O N (Brafcmate StuMes.
1 x
ACC. No DATE
ELECTROLYTIC IRON..
A STUDY OF THE PRODUCTION OF IRON BY ELECTROLYSIS, WITH SPECIAL
REFERENCE TO ITS RECOVERY FROM SULPHIDE ORES..
THESIS
Submitted by
WILLIAM RAYMOND MoCLELLAND
As Part of the Requirements for the Degree of Master of Soienoe.
MAY L925.
MoOILL UNIVERSITY, MONTREAL, CANADA. ELECTROLYTIC IRON.
A Study of the Production of Iron by Electrolysis, with Special:
Reference to its Recovery from Sulphide Ores.-
PART I.
Introduction
Historical Outline and Descriptive*
Physical Properties of Electrolytic Iron.
PART II
Theoretioal Considerations.
A. Leaohing.
B. Electrolysis.
PART III.
Experimental Research.
A. Ore Body and Treatment of Ore.
B. Leaching.
C. Electro-deposition.
General Summary and Conclusion.
PART IV.
Appendix.
References.
Sample Calculations.
Bibliography. (1)
PART I.
INTRODUCTION.
Iron, is the oommonest, most widely used, and at the same time the most vitally important of all the base metals. In the growth and developementr of modern civilization it assumes a dominant position..
Iron was not unknown to the anoients,nor were they unaware of its uses.
As early as 1500 B.C.. the inhabitants of India; fashioned swords and spear heads. They even recognized, its qualities: for purpose* of construotion.
Wrought1: iron beams measuring twenty feet in length have been found in the temple of Kanaruk dating from 1250 B.C.
The metallurgy of iron at this period was extremely primative and continued so for many hundreds of year.s. It v;as notr until the sixteenth century that the introduction of-the air blast into the furnaoff made the progress of iron manufacture comparatively rapid.From thi'a period on, tha production increase-d. In US1* Henry Cort invented tha " puddling, process'1' for the manufacture of; wrought iron.. This was an advanoe step and greatly oheapenei the production of iron* In. the nineteenth century the famous researches and inventions of Sir Henry Bessemer, Sir William Siemens and others laid the foundation of the present day steel industry.
The increasing demand for iron in all its numerous combinations has given impetus to the developementf of new metallurgical processes for its recovery.. The utilization of low grade ores and ores unsuitable for smelt ing has opened up further fields of. researoh and investigation.
Coincident^with this increased demand for iron has been the depletion f of the world's supplies of fuel. This has to a small extent been ofset by the tremendous strides that have been made in the utilization of electrical energy during the last half oentury. (2).
These facts have led many investigators to examine the possibilities of producing iron by eleetrical means. Two methods of recovery suggest themselvesJflrst, that of smelting where eleotrieity furnishes the required heat;: and seoond, by electrolysis from a solution obtained by leaching the ore.
The first method is satisfaetorily employed in Sweden,1 where ohsap electric power, searoity of fuel, and high grade ore make such a process economically possible. The seoond method , that of electrolysis, has the advantage of producing a product of extreme purity and further ef utilizing ores whleh are not suitable for smelting; e.g. the sulphide ores of iron.
Neither of the above methods can at the present time compete with the ordinary blast furnace. But for special purposes and under peculiar conditions they can add materially to the world1* supply of iron.
It is the object of this thesis to investigate the problems of leaching pyrrhotite ore with ferrie chloride, and the production of iron by eleotrolysis of the resultant ferrous chloride solution
The physioal properties of pure iron make it highly suitable for many metal products. Eleotrolytlo iron is used for boiler tubes, pipes in refrigeration machines, magnetic cores for electrical apparatus, use in alloys, eleotrioal transmission wires, etc.
HISTORICAL OUTLINE AND DESCRIPTIVE.
Eleotrolytlo iron has engaged the attention of investigators for many years. Probably the first to produce it was Bookbushmann in lffM-6.
He deposited on a copper matrix a plate of iron 150 millimetres square and
2 millimetres thick.
In 1&60 at Petrograd, the Russian chemist Klein succeeded in making blocks of eleotrolytlo iron. These were used as plateB for the printing of bank notes. The bath used was a solution containing 5 per cent of iron sulphate and 5 per oent of magnesium sulphate. The solution wan kept neutral by the (3) addition of magnesium carbonate. A low ourrent density was employed of 0.1 to 0.2 amperes per square decimetre.
Feuquieres in 1S67 exhibited at Paris some galvanio deposits of iron, but his prooess was never divulged.
The German firm of Merk in 1900 patented a prooess based on the elec trolysis of highly concentrated pure ferrous ohloride. A. ourrent density of
J to ty amperes per square deoimetre was used and the solution was kept: at a 7 temperature of 70 C. Burgess and Hambueohen in 190*f produoed successfully quite a large quantity of electrolytic iron from a bath of a double sulphate of iron and ammonium. The temperature of their solution was kept constant at 50 0V and the ourrent density employed was 1.0 ampere per square deoimetre.- The* work was carried out in the laboratory of Applied Electrochemistry at the
University of Wisconsin.
Numerous trials were run using- a large number of eleotrolyfces, butr the double salt of ferrous ammonium sulphate was found to be the most satisfactory. The voltage was a little under 1.0 volt. The anodes were of wrought iron or steel and the cathodes of sheet iron with their surfaces carefully cleaned and smooth.
From this series of investigations they found that the yield was about
2*2. lbs. per K.W. hour of 99.9^ pure iron. The deposited iron was very hard and had a very high melting point. Hydrogen was evolved on annealing from under 100 C. to a dull red heat.
They consider that the hydrogen may be in the metal either as a hydride or simply as a condensed gas. Quantities of hydrogen to the extent of several hundred times the volume of the iron have been found.
About the same time as the work of Burgess and Hambueohan,, Professor
Foerster of Dresden carried out some investigations in this, oonneotion. The solution whioh he used was a slightly acid one of iron sulphate* It was keptr at a temperature of 95 C. andi a ourrent density of 2?«0 amperes per square decimetre.
In 1907 Cowper-Colea patented a prooess employing, ai 20^ solution of sul^hocresylate of iron. Brisfly the prooess oonsists in leaching iron sorap or finely divided iron ora> with aoid» The leaching is aided by employing a small /o ourrent and using an insoluble anode materiad.
The eleotnolytej used for the deposition cells oonsists of a 20$ solution, of: sulphooresylio acid saturated with iron. The iron, is deposited on revolving mandrels. These are coated with a thin deposit of lead. On the lead, the iron deposit oomes off in the form of a tube. The temperature of the solution is about 70 C. and the ourrent density: alxout 100 amperes per square foot. The solution.is kept oharged with iron oxide. No explanation is given for this, but the writer understands that a similar oondition is maintained in the cells at the works of the Company " Le Fer " , G-renoble,Franoe.. The reason given,is that a more satisfactory deposit is obtained,due to the oxide reducing the aci dity of the solution and further serving as a. meohanioal polisher to the depos- iting surfaoe..
Various German patents were granted in 1909; one of which specifies the use of highly concentrated solutions of iron ohloride and oaloiura ohloride.
The temperature of these solutions was 110 C. with a ourrent density of 20 am peres per square decimetre.
1910 saw the first successful attempt to manufacture eleotrolytio iron on a commercial soaie.. The Company "'Le Fer" of Grenoble,Franoe. took out
/3 patents for its manufacture. The prooess in principle oonsists of electrolysing a solution of neutral ferrous chloride and depositing the iron on cylindrical revolving cathodes. The anodes are of oast iron. The deposit is 99*97^ pure. It is first (5)* annealed to remove the occluded or combined hydrogen. The tubes are then turned. in a lathe, against a blunt tool whioh stretches and loosens the deposited; iron and it is then easily removed from the mandrel. These tubes are used as boiler tubes. They can be drawn tx> any required size.
Dr. L. Guillet gives a comprehensive aocount of this prooess in the
Journal of the Iron and Steel Institute, Vol- 90. 191^«
The average composition of the iron after removal of the gases by annealing is as fellows:-
Carbon. OJdQ^fi
Silioon , . .0.X>07?o
Sulphur <...0.006>
Phosphorus O.OOff^.
Iron 99.97^
By the aid of oertain operations and modifications ir* the electrolyte the phosphorus content was gradually reduced from 0.200$ in. 1911 to O.QOg^o in
191^.
The pig iron used as anod9e has the following analysis:-
Carbon ?v35^
Siliaon l*31/«
Sulphur Q.QJfi
Phosphorus. •..... 1.07/a
A current density of 1000 amperes per square metre yields per kilo watt-year two tons of metal, inoluding cost of power for meohanical details of the plant , particularly the rotation of the cathodes*.
The metal as deposited is extremely brittle due to the ocoluded be hydrogen. But by careful annealing this canAentirely removed and very duotile tubes obtained. The ourrent praotioe is to manufacture tubes of four metres in length, diameter of one to two hundred millimetres and with a tniokness of
0.1 to 6.0 millimetres* At the time this paper of Dr. Quillet's was written the ontputr was onee hundred tubas per day. At the present time the daily outputs is about one and a half tons of. broiler tubes ready for the market. The variation of gauge amounts to no more than 0.002 inches plus or minus*.
Air blown through tiie electrolyte? causes agitation of the slimes and absorbs some of the hydrogen, in the solution. Further it slightly oxidizes the solution causing the formation of iron oxide which aids in producing a smooth surface 021 the depositing iron.
The only ccmmeroial plant for eleotrolytlo iron at present in operation 14- in the United States is that of the Western Electric Co* at Hawthorne, 111. The electrolyte is a solution of ferrous sulphate and ohloride and ammonium sulphate. The anodes are of mild steel and the oathodes polished sheets of steel. The ourrent density used le about 12 amperes per square toot.
The brittleness of the iron is made use of in this prooess. When the depositr has reached a thickness of an i to at of an inch , it is stripped off and powdered in a ball mill. The hard finely powdered iron is pressed into magnet cores.- These are subjeoted to heat to remove the oooluded hydrogen., leaving cores of pure iron partioles. The capacity of the plant is anout two tons per day..
With the exception of the prooess invented by Mr. Qswper-Coles, all of the foregoing descriptions are of refining processes. Different electrolytes, varying ranges of solution temperatures, and a variety of ourrent densities and voltages have constituted the main differences between, each process
The experimental work of this thesis deals with an investigation of is the Eustis Prooess. This is a reduotion process, and has been patented by
Messrs. Eustis and Perrln of Boston, Mass. It is based on the chemical equation
2 FeCl^ + FeS - 3 FeCl2 + S.
Pyrrhotite ore, which may be considered approximately FeS ( it is given as Fe,Sn+i > where n^# or 11.) is leached with a solution of ferric ohloride. The ferrous sulphide breaks down, sulphur is preoipitated and the solution is reduced to ferruos chloride. (7).
Copper sulphide in the ore will react with ferric ohloride as follows:-
CuS-f- 2FeCl — CuCl2 -+• 2FeCl2 -K S.
The oopper is removed from the solution by passing it over scrap iron in cementation tanks. The resultant solution of ferrous ohloride is electrolysed in a two compartment oell.The cathode, a revolving steel mandrel, is separated by a diaphragm of asbestos cloth from the anode oompalftment. The anodes are of graphite. As the electrolysis proceeds the solution in the anode compart ment-becomes f err io chloride,( this will be described in detail later).
This is drawn off- and used for leaohing fre«h ore. The prooess is a oyolio one. Ae^ahown by the equation sulphur is liberated in the reaction and may be reoovered as a by-product. The iron whioh deposits on the cylindrical cathodes can be used as formed for tubes, or out and rolled into sheets.
The application of this prooess has been tried out on a zinoy pyrrhotite 17 tailing by the Consolidated Mining and Smelting Co. Ltd., Trail, B.C. Very encouraging results have been obtained.- Rolled samples of this iron show a product of great purity and highly duotile and malleable. Analysis gives only 0.0^ Zino present.
The leaching is oarried out in laboratory Dorr agitators constructed of wood. The rate of solution is found to be direotly a function of the temperature and the fineness of the ore.
The deposition cell is divided into three compartments, the central one being that of the oathode. The anodes are of oarbon. The oathode is rotated at a peripheral speed of 125 feet per minute(51+5 r.p.m.). The tamperature of the electrolyte is maintained at or above 75 degrees C; The ourrent densities employed varied from 100 amperes to 50 amperes per square foot.
The voltage for the latter ranging from ^.2 to ^.5 volts. The ourrent efficiencies obtained ranged from 85% to 95fo. The removal of impurities, largely lead and zino, previous to electrolysis was done by preoipitating them with H S gas and neutralizing the solution with CaCO,. (ff).
An investigation, on the eleitro-deposition of iron has recently been carried out by W.. F. Hughes, late Chief Research Chemist, Electro-iletallurgical
Committee, British Ministry of Munitions.
The depositions were made from an iron ohloride bath. The object of the work was to determine the effeoir of temperature, ourrent density, and movement of oathode or electrolyte on the structure of the deposited iron. The results obtained are of considerable interest and importance, but as they deal largely with the physical properties of electrolytic iron they i ft will be discussed under this heading.
PHYSICAL PROPERTIES OF ELECTROLYTIC IRON
Eleotrolytlo iron is u. white and in most oases extremely hard 19 and brittle metal. The Brinnel hardness is about 195. The brittleness is due to oooluded hydrogen. By employing oertain ourrent densities a comparatively malleable deposit can be obtained. But the usual practice is to anneal the deposit. The hydrogen is easily driven out. The resultant metal is extremely duotile and malleable. Previous to annealing,the surface of electrolytic iron shows a strong tendency to oxidize in the air.
Tho tendency for eleotro-deposited iron to absorb hydrogen is illustrated by a sample made by the Cowper-Coles process, which was found on removal from the bath to contain 0.**5/o of hydrogen. At 500 degrees C. the sample contained 0.020;i and at £50 degrees C. 0.002^ remained. Sir
Robert Hadfield examined a speoimen and on heating it in a vaouum between
800 to 1100 degrees C. for four hours and then raising it to the neighbor hood of l*+00 degrees C. for a further two hours he found that J>h gms. of the iron had a volume of 4-3 cu. om. and yielded 28.8 ou.oms. of gas with the following composition:- (9).
Hydrogen.••••••••••••.•••••• l8*8fo by volume•
Carbon monoxide. •••• 7.4% " "
Carbon dioxide 0.2^
Nitrogen.. „ 2.2^ H
Oxygen. •••••••••••••• •••• Nil.
After annealing the iron has a Brinnel hardness of 90, the annealing being carried out in a bath of magnesia at a temperature of 900 C.
The tensile test gives a breaking strength of 50»# Kgs. to 3.2.£ JCgs. per. sq.mm. and an elongation of Ho.2 to *+2.1<£ in the direction of the axis of the tube. Compression tests show that they can undergo an extraordinary degree of. deformation without fraoture.
Tests on the electrical resistivity of annealed electrolytic- iron gave a result of 10.22 microhms per ou.om. The iron tested had a phosphorus content of 0JZ25% and 0.011^ of arsenic. According to Benedioks these impunities would oause an eleotrioal resistivity of 0.2M- miorohms per cu.om. Therefore the above figure could be reduced to 9*9& miorohms, whioh may be taken as the electrical resistivity of pure annealed eleotrolytlo iron.20
Mr. Bradley Stoughton of New York in a recent artiole gives some figures regarding the properties of eleotrolytlo iron as produoed at
Grenoble, France. The purity of the iron has already been mentioned as
99.97/£ Fe. Tests on the meohanioal properties of the tubes were made by the
National Tube Co., the General Electric Co., and in the laboratory of
Columbia University.
The results obtained were as follows:- (10).
Ultimate Yield po:in t Elongati on Per oent Remarks. strength lbs./sq • in. Per oent. Inches. reduction lbs./sq.in. of area.
72600 1.0 2 Cold rolled.
76*500 #.0 ^ As received.
578T00 0.5 2 Cold rolled.
62000 52000 12.0 8 50 As received.
385Q0 0.5 1 Cold rolled.
39000 27000 30.0 8 60 Annealed.
4-lffOO 35.0 *+ Annealed.
The bursting strength of a Grenoble tube 4- in. in diameter and
0.03 in. thiok was 1110 pounds, corresponding to a fibre stress of 73500 lbs. per sq. in.
The annealing mentioned in the above table was oarried out at a temperature of 900 degrees C. for twenty minutes. The oold working properties of the Grenoble tubes are exceptionally good. It is the regular practice to draw through a die five times without annealing. The customary praotloe with soft steel is to anneal before eaoh draft.
Some tests on the resistance to corrosion of this iron which have been made at the Massachusetts Institute of Technology showed that a pieoe of Byer's wrought iron pipe corroded, nearly twice as fast, and Shelby steel tubing 2.6 times as much in the atmosphere as eleotrolytlo iron made by the Eustis prooess. An immersion test of twenty two hours in 5^> solution of HSO gave a ratio of loss of weight per unit area as follows:-
For eleotrolytlo iron( Eustis ), 1.00
For steel ••••••••.••.•••••••••. M.25
For wrought iron •••••••••••••••, 18.50 (11). zz Three series of experiments were carried out by W. ITiHughes in, his work on the electro-deposition of iron.. In the first series of exper iments- he studied the effect of temperature* The ourrent density was kept constant at 120 amperes per sq;. ft. and the time was two hours. The cathode was either a steel rod thinly coated with oopper in a oyanide bath, or a copper rod.. The anodes were of Swedish, iron..
At 70 degrees C. the deposit was dark and powdery and after- about twenty minutes split up and became useless. At 90 degrees C. a maorosoopio examination showed a good smooth and bright deposit. It was found to be hard and brittle. The voltage was 0.9 volts. The deposit at lOOdegrees C. was good in colour and smoothness. At 110 degrees C« the deposit was good and light gray in oolour.. The texture was close and even. There were no outgrowths or lumps and no brittleness shown on sawing.
The general oonolusions from this series of experiments show that as the temperature is raised the deposit becomes light in oolour and smooth till a temperature of about 90 degrees C. is reaohed. As the temperature is further raised the deposit becomes more1 ooarse-grained and crystalline.
The effect of rise of temperature with constant ourrent density is to change the deposit from a fine-grained to a ooarse-grained one, that is from a visually non-crystalline to a visually crystalline deposit. These general oonolusions are further substantiated by a miorosoopio analysis of the deposits. The coarser the grain the less brittle and hard is the deposit.
The second series of experiments vai« carried out at a constant temperature of 110 degrees C. and varying the ourrent density.
At a current density of 60 amperes per sq. ft. a good,even,light- ooloured deposit was obtained. It was very finely crystalline and had no lumps or outgrowths. At 160 amperes per sq. ft. the deposit' was light gray, smooth and crystalline. At 200 amperes per sq. ft. the oolour was as above but the deposit was more coarsely orystalline and quite malleable. At 24-0 (12). amperes per sq.. ft. the deposit was light gray in oolour and rather rough.
It was more coarsely crystalline: than the two previous deposits. It was not malleable,but powdered under hammer blows.
The general conclusion on the effect of current density is that there is a gradual inorease in the nature of the deposit from finely to coarsely crystalline as the current density is increased. The size of grain inoreases as the ourrent density rises from 60 amperes per sq. ft., until a. maximum grain sire is reached somewhere in the region of 120 amperes per sq. ft. The size then diminishes to a minimum somewhere between 120 and
200 amperes per sq. ft.-It again becomes larger at the highest current densities used.
The third series of experiments deals with the effect of meohanioal movement on the deposit. In some cases a revolving oathode was used, in others a stroke movement was employed.
The general oonolusion drawn from the maorosoopic and miorosoopio examination of the deposit is that meohanioal movement tends to deorease the size of the grain.. And it further shows that the predominating type of structure of deposits from moving cathodes is fibrous.
These series of experiments show that the concentration of available metal atoms at the oathode surfaoe is the dominant factor in the deposition, temperature and ourrent density being contributors. This agrees with theoretical considerations.
Iron is one of those metals whose cathodio deposition encounters strong irreversible reaction resistances. This fact favours preferential discharge of hydrogen ions. Thus for satisfactory deposition the ratio of Fe— H must be kept as high as possible. That is , the iron concentration 23 must be large and the hydrogen concentration small. (15) PART II. THEORETICAL CONSIDERATIONS
A. Leaching.
Leaching may be defined as a ohemical reaction in which a solid substance la brought into aqueous solution. The term is applied in general to all hydrometaliurgical treatment of ores.
Leaching of ores is in general dependent on the following factors, namely, the fineness to which the ore is ground, the temperature: and concentration of tne leaching solution or solvent. Extraction or solubility is directly proportional to fineness of ore and increase of temperature of. solvent.
When iron sulphide is treated with a solution of ferric ohloride the. iron sulphide breaks down precipitating sulphur and reducing the solution to ferrous chloride.
FeS + 2 FeCl3 = 3 FetCl^ + g
This is a typical leaching reaction and is the one upon which the.
Euctis Prooess is based.
One of the faotors mentioned above as conducive to the optimum conditions for extraction is limited in this reaotion, viz. temperature.
The iron sulphide can be ground to the minimum of size tut the temperature of the solution cannot exoeed certain limits. The reason for this lies in the properties of ferric ohloride.
Ferric- onloride is a yellow deliquescent hydrated salt commonly denoted by the formula FeCl} . 6 HgO. It has numerous modlfioations depending on the number of combined water molecules. The anhydrous, salt is made by passing 24- chlorine over heated iron when it sublimes in dark scales. Commercial ferric chloride, known as iron perohloride is made by treating iron with hydroohlorio add in the presence of air. (1*0
Aquous solutions of the salt react strongly acid. This is due-to the A feebly basic? properties of ferric hydroxide and the faot that the salts are; to some extent hydrolytioadly dissociated. Hydrolysis; increases with dilution and rise of temperature.
FeCl^ + 5 %0 -z> Fe( OH)^ + 5 HC1
This is observed by the faot that the yellow color of the undissociated ferric ohloride disappears and gives plaoe to the red-brown color of the colloidal ferric? hydroxide which is formed. If this hydrolysis- is brought about by increasing the temperature of a dilute solution of FeCl»> it can be again oonverted into Feci* solution by being kept at a lower temperature for several days. Z5
By increasing the concentration of the salt in aqueous solution the. tendenoy for the colloidal ferrio hydroxide to precipitate is diminished, until the boiling point of the solution is reached when the hydroxide wiii precipitate.
With dilute solutions the preoipitation takes plaoe at temperatures below the boiling point. In very dilute solutions preoipitation takes plaoe on stand ing for a period of time at room temperature.
The reaction is no longer reversible when onoe the hydroxide has ceased to be colloidal; and precipitates as a hydroxide or complex oxyohloride.
This property of ferrio chloride must be borne in mind when employing it as a solvent and as a consequence of its hydrolytio tendencies the leach, never should be heated above 1D0°C
The reaotion between ferrous sulphide and ferrio ohloride is exothermic?, 26 producing about 700 B.T.U. per lb., of iron dissolved. This faot aids in carry ing out leaching operations.
Iron sulphide is not alone in being aoted upon by ferrio ohloride bufr both cuprous and ouprio sulphides,and to * small extent* sulphides of lead and zino are acted upon in a similar manner. (15)
The reaotions for ouprio-sulphide (CuS) and cuprous sulphide; (Ctuff)
are as follows:
CuS + 2 FeCl^ = CuClg, + 2 FeC^n- &.
Cu^SB + 2 FeCl^ = 2 CuCl + 2 FeCl^ + S.
Cu2S + ** FaCl^ = 2 CuQI^ + 4- FeCl^ + &• 27
The removal of the copper from the solution is effected by passing the
solution over sorap Iron.
CuCl2 + Ffc = du + FeCl^.
2 CUC1H- Fe = 2 OU + FeGl^ zi
The copper deposits on the iron loosely or preoipitates in accord with
the above equation. The method of freeing a solution from copper is
comparatively simple. Greater difficulty is met with in removing zino and
lead from a ferrous chloride solution. One method is to precipitate these elements with H^S and neutralize the solution with calcium carbonate.^ Thia method has been carried out and has been found to be quite satisfactory.
The conditions whioh are essential for leaching aulphide ores with ferric ohloride are the following:
a. Fineness of the ore.
fc. Concentrated solution of ferrio ohloride.
*e Temperature of solution to be kept below 100°<3.
d. Absenoa of oxidizing conditions in leaching.
e. Agitation of ore; and solution. (16)
B. Theoretical Considerations Involved in Electro-Deposition*
Eleotrolysis and consequent electro-deposition is dependent on certain chemical and physioal phenomena. Primarily it is due to dissociation and ionization; the breaking up of the molecules in the solution into iona or charged atoms.
Faraday's laws of electrolysis, give the relation between time, ourrent- and quantity of element deposited in an electrolytic reaotion. Tha quantity of electrioity required to deposit one gram equivalent of an element ia 96600 coulombs. From this figura it is found that in one ampere-hour 1.04-2 grams 29 of iron will be deposited.. The electrolysis to be considered is that of a solution of ferrous chloride* When an electric ourrent is passed through such a solution the following shows diagrammatioally the. reactions taking plaoe and the resultant produots.
Cathoda FeCl^ + 2 HgQ (In solution). Insolubla Anodes.
Fe. + 2 CI + 2 H + 2 OH. (Dissooiatod into iona).
2 OHi - HgO + t 02 L Fe. «- Ffc *J + K9 «- 2 H <- 2 01 — CI,
G%.-fl£FeGl2 = 2 FeCl*
The: iron deposits as metal at the cathode-* as does the hydrogen. A.
large amount of the liberated H2 i8 oooluded in the iron, the remainder, being evolved as gas at the oathode surface.
Oxygen gas is evolved at the anode. The ohlorine atom which forma at the anode immediately combines with a molecule of ferrous ohloride forming ferrio chloride. Hydrolysis, may occur as previously discussed under the (17) properties of ferric ohloride.
When the anode and oathode are separated as in the diaphragm cell the foregoing reaotions take place. But it is essential that a small flow of electrolyte be maintained through the cell. The ferrous ohloride solution enters the oathode compartment. Dissociation takes plaoe and the ferrous ions migrate towards the oathode, as shown.. The ohlorine ions migrate to the anode through the diaphragm. Trery soon the anolyte becomes quite yellow due to the formation of ferrio ohloride. To prevent: any diffusion of ferrio salts into the catholyte, a hydrostatio head should be maintained in the cathode oompartment. This need only be very small. For It was found that after a run where the solutions had remained in the oell for over half an hour, that the oatholyte regained the usual green color, while the anolyte was deep orange-. This shows that there is little diffusion through the asbestos diaphragm. But the diffusion would be somewhat accelerated by the agitation due to the revolving oathode, and for this reason a slight flow should be maintained.
The eleotromotive foroe is the next factor to be considered. The voltage measurements are always across the two electrodes of the cell.
The decomposition voltage of a solution of ferrous chloride is tne
Concentration of the solution is a factor and the figure obtained is that of a normal ionic solution. This voltage for ferrous ohloride is 1.757 30 volts. (ET0= %e - Eal2 = .065 - ( 1.694-) -- 1.757). A voltage over this amount must be employed to deposit iron from such a solution. This assumes that the electrodes are insoluble. When an iron anode is used the decomposition voltage is theoretically zero. The solubility of the anode acts as a depolarizer and prevents the electrode potential of 31 the anode from being established. (18) A phenomenon of considerable importance in electrolytic^ work, is overvoltage. This is defined as "the potential neoessary in excess of the reversible^potential ( i.e.. electrode potential) to disoharge the produot in question4*. It is largely affected by ourrent density. The gases liberated from the electrolysis of an aqueous ferrous ohloride solution are hydrogen, oxygen, and ohlorine. The ohlorine overvoltage need not be considered; for the solution acts as a depolarizer or absorber, inasmuch as soon as the atom forms it immediately combines with the ferrous chloride to form ferric ohloride. With a. ourrent density of 1.5 amperes per sq.cm. at 25°C: against an iron electrode the over• voltage for hydrogen is given as 1.29QJ? volts. Oxygen with a similar current density and at the same temperature has an overvoltage of 1.2&2 volts against 33 a soft graphite anode. These figures are from a very reoent series of investigations oarried out in the Electrochemical Laboratory of the Massachusetts Institute of Technology. The importance of hydrogen overvoltage lies in its bearing on the liberation of gas at the cathode. The liberation of gas lowers the ourrent efficiency. Therefore it is essential to operate at a voltage which will not be sufficient to literate the gas, i.e* a voltage less than the sum of the electro-affinity and the overvoltage. This can only be accomplished when the decomposition voltage of the solution in question is lower than the sum of the overvoltage and electrode potential of the hydrogen. VTith regard to a ferrous ohloride solution,these two values are so olose together that it is almost impossible to prevent the liberation of hydrogen at the cathode. To reir.ee the hydrogen concentration to a minimum it is essential to keep the solution free from any free aoid. Polarization is the e.m.f. caused by the products of eleotrolysis whioh opposes the applied e.m.f. of the cell. This faotor figures largely in the (19) diaphragm oell and when an insoluble anode of graphite or carbon is used. As gases are liberated at the electrodes a thin layer of gas bubble* forma* These constitute a cell which tends to set up an e.m.f• opposing the e.m.f. of the cell proper.. In the two compartment or diaphragm cell oonoentration polarization is an important factor. In the anode compartment the solution oonsists of a- mixture of ferrous and ferrio chloride. In the oathode compartment the solution is ferrous ohloride. Nernsfr has derived a formula for obtaining the value of the e*m.f • due to difference of oonoentration. E = .058 X ~—~ - log -1 u =. velocity of anion. v = M w cathion. x. = valency. C^ = concentration of anolyta* C£ = * * oatholyte. This e.m.f.. will oppose the applied e.m.f. The resistance of a oell is increased by lowering the oonoentration of the electrolyte. The resistance on the other hand is reduoed as the temperature of the electrolyte is raised. The foregoing paragraphs have dealt briefly with the ohemioal and eleotrical aspects involved in eleotrolysis and the conditions bringing about electro-deposition. A recent paper by W.* E., Hughes gives some interesting information in regard to the formation of electro-deposits in their relation 35 to crystalline structure. The analogy between ordinary crystal growth and the growth of an eleotro-deposited method is very marked. Slow cooling of a rook magma or a salt solution will oause the formation of large orystals, while rapid cooling makes for the formation of small crystals. (20) With regard to metals this also holds. "'Tha number of crystalline grains of whioh a oertain mass of metal is oomposed must depend upon the number of 37 centres or nuclei at which crystallization begins.M The oonolusions drawn by Hughes from the considerations of mineralogy and metallurgy oited above are:- 1. "That there is direot relation between rate of oooling and size? of grain or crystal; 2. Quicker oooling produces a greater number of orystal nuclei, resulting in smaller crystals; 5. Crystals already in being grow where rate of cooling is slow.*' Applying these oonolusions to electro-deposited metal, he says that - 1. There will be a.direct relation between rate of deposition and size of grain, or orystal; 2. Quicker deposition will produce a greater number of orystal nuolei resulting in smaller crystals;. 5. Crystals already in being will grow Wx.ere the rate of deposition is slow. Great concentration will lead to fine struoture while low oonoentration will lead to coarse structure. "'The struoture depends upon the concentration, of the orystal-forming atoms in the immediate neighbourhood of the cathode.* The two factors obtained from this conclusion whioh govern the type of struoture obtained are: 1. The rate of discharge of the metal ions. 2. The availability of the resultant atoma for graiii formation. The steps from ion to orystal are given by H.. Freundlioh and I. Fischer1, as follows:- (21) "Metal ion (charged and hydrateot) —* discharged hydrata —> metal atom —> metal crystal.* 38 The transition from atom to crystal is the one with whioh this study is most concerned. A.number of theories exist as to whether or not the formation of the deposit is a single step or process from the atom. Will they form, new orystal nuclei or aid in the growth of grains already exist- ing? The answer suggested is "that it depends upon the concentration of the atoms, and that only."' In the diagram illustrating the eleotrolysis, it was shown that the oxygen* due to the dissociation of the water, is liberated at the anode.. Now if dissolved oxygen Is present in the solution (i.e. dissolved from the air in the water originally used in making the solutions) it will be liberated with the iron at the oathode. This would oause the formation of oxide in the deposit* (22).- PART III- EXPERIMENTAL RESEARCH. A.. Looation of Ore Body and Treatment of Ore. The ore used in the experimental work was a pyrrhotite from the Memphremagog Copper Mine, Knowltons1 Landing, P.Q.. The mine is situated seven hundred feet above the level of Lake Memphremagog and is one and a half miles from Knowltons' Landing, in the Eastern Townships of Quebec. The ore-body is in Cambro-Silurian, and the region is oomprised of a mixture of argillaceous and ohloritlc schists or slates and dykes of ool-u^nar trap. The mineral lodes run in thj direction of NJD.. by S.W. with a dip to the west of 30 degrees. The main vein has an average vridth of from 25 to ?0 feet. The foot wall of the lode is oomposed of massive trap rock and the hanging wall of schists or slntes. The lode is oapped with bfcown hematite 4 feet to 8 feet in depth. Then black sulphides 2 40 feet to 3 feet. These are followed by the yellow sulphides. The sample of ore supplied for the tests was high grade pyrrhotite oontaining little gangue material. Seventy three pounds of the ore were crushed, first in a Dodge breaker and then in rolls to pass -£- inch mesh. The produot was sampled in a Brunton sampler to a ten pound working sample. Amounts of ore were taken from this sample as required and ground in an earthenware ball mill using silica pebbles to pass a -200 mesh soreen. A complete chemical analysis of the ore was carried out giving the following results:- Iron — —51.16 y0 Copper 1.50 Lead -i Trace Zino — 0.67 (23)- Silica -----2.8T0 Alumina 1.16 Caloium oxide —1.60 Magnesia — —— ——-0.0 Sulphur ------.——-..--36.21 B. Leaching Experiments. T.ie theoretical considerations involved in leaching pyrrhotite ore with ferric chloride have already been disoussed. The first consideration in the experimental work after the preparation and analysis of the ore was to determine the factors involved in the leaching and further to establish the necessary assumptions. The following assumptions were made :- FIRST. The formula for pyrrhotite was assumed to be FeS. SECOND. It was assumed that all the iron in the ore was in the form of sulphide. THIRD. The sulphide was taken as the monosulphide of iron (FeS). The factors involved in the leaching experiments are:*- 1. Temperature of leaching solution. 2. Agitation of leach. 3. Size of ore particles. 4-.- Concentration of ferrio ohloride solution. 5. Quantity of ore used. 6. Time. The size of ore particles was limited to —200 mesh. This was in aooordanoe v/ith the laws of solution, viz. that th) finer the solute the greater the action of the solvent. The agitation was also a constant faotor. The objeot was to keep (24)- the ore well mixed with the solution and prevent any settling at the bottom, of the containers. The speed of the paddles varied from about a hundred to two hundred R*F.M. and was governed by the quantity of ore present. The temperature of the solution* the concentration of ferrio chloride, the relative quantity of. ore per test and the time are the variable faotors. The following data is from the results of experiments, oarried out to determine the effect of these several faotors on the leaching of the ore. The leaohing tests were oarried out in wide-mouthed bottles of about 650 o.o.. capacity. Fig. H. Plate No.l. shows the set-up of the apparatus. The bottles (b) were kept in a water bath (a).. Glass paddles (g), causing the agitation, were connected by a belt from pulleys (c) to a small table motor (f). The glass paddle rods worked in a glass-tube bearing through the oorks (m). The pulleys were of cork and fitted tightly to the glass rods. A constant temperature was maintained regulating the Bunsen burner (h). A thermometer (d) recorded the temperature of the bath. The objeot of the leaohing experiments was to determine the most favourable conditions of temperature and concentration for the complete extraction of iron in the ore. Commercial ferrio ohloride, known as iron perohloride, was used to make up the leaching solution. The salt contains between 41 1 ft to 2 Jo of free hydrochloric acid. A test on the amount of ferrous iron present gave 0.79 fo* It was neoessary to filter the solution before using it in the tests. A considerable amount of hydrated oxide and hydroxide of iron rendered the solution murky. Clear liquid was always used. No. I. Diagram of S/na// Leac/7/ng f/f>/oarafus D/agrani of Large. Leach/na ffpparafas. Ca/yQCify of Jctr i. b 1 f/t^t . s~+ £i (25).. The method of calculating the concentration will be found in the Appendix, Part 17. SERIES A. This series of experiments was of a preliminary nature. The ore used was a pyrrhotite analysing 42.5 % Fe. Some leaohing tests were oarried out with this ore in the previous year by the writer. Fiv-a gram samples (- 200 mesh) were agitated with different cone 3iit rat ions of ferrio ohloride for five hours at room temperature. The ore was not conoentrated and in all tests non-oonoentrated ore was used. The speed of the paddles was about 120 r.p.m. The volume of the solution was 650 CC. At the completion of a run the residue was allowed to settle for several hours. A 10 CC. sample was removed by a pipette and analysed for iron. The total amount- of iron in the final solution less the original iron in the solution gives the amount extracted from the ore. The concentrations of ferric ohloride were very low. In each run the figure was doubled. Table I shows the results of this series. TABLE NO. I. Iron in 5 grams of ore 2.125 gms. Volume of solution -— -650 o.o. Test. Conei. of FeC13 Temp. Increase in Per oent of. iron in ^ms./lOOOo.o.. ironin ^ras. ir. ore extraoted. 1.. 1..9 20 .195 9.2 fo 2. 3.8 20 .195 9.2 % 5. 7.6 18.5 -325 15.3 % 4. 15.2 20 .390 18.3 $ 5. 30.^ 19.5 .475 22.3 % (260. Discussion of results. 1. At completion of the run. the solution contained a br.omi flocoulant-precipitate. On settling the solution was almost oolour- less. The praoipitate was soluble in HC1 • It was probably ferrio hydroxide caused by hydrolysis due to the very low concentration- of ferrio ohloride.r 2., Less hydrolysis than in test No. 1. 5.. Settling of residue much more rapid than in previous run. No observed hydrolysis. 4-.. Nc colour ohange in solution and no visible hydrolysis. 5. Si:iiilar to test No. 4-. The general results show a very low percentage of. extraction. Series B to E were run using the new ore, analysing 51.16 % iron. Five gram samples of ore were used in eaoh oase with varying concentrations of ferric ohloride solution; and at temperatures ranging from 17 degrees to 70 degrees C. The primary objeot was to determine the effect of temperature on the extraction of iron from the ore. The speed of the paddles in Series B was U80 r.p.m. and about 200 r.p.m. in the remaining series. The following table gives the results of these tests. TABLE NO. II. Iron in 5 grams of ore- 2.56 gms. Volume of solution 650 e.o. Time of test 5 hours. Test and Cone, of FeCl} Temp. Inorease in Percent of iron Series. in gms./lOOOo.o. degrees C. iron in $ms.. in ore extracted. 1. B. 50.** 17 0.670 26.2 f> 2. B. 6*2.1 17 1.04- 40.7 $ 3. B. 164.2 17 0.72 27.9 $ 1. C. 15.2 50 1*95 76.2 % 2. C 30.4 50 1.8k 71,9 fi (27). ( Table II. oontinued.) Test and Cono. of FeCl,. Temp. Increase in Per oent of iron Seri es. iron. in ore extracted. 1. D. 15.2 60 1..69 66 % 2.. D. 36.6* 60 2.28 89.2 f0 3. D. 82.1 60 2.21 86.4 f0 4. D. 147.1 60 2.28 89.2 fi 1. E. 36.8 70 2.28 89.2 % 2 .. E .' 147.1 70 2.04 80.0 % Disoussion of Results. Series B* No.l. Small percentage of extraction. No visible hydrolysis. Tests 2 & 3 similar to No. 1. The general results show that the extraction is dependant on tue oonoentration of the leaohing solution, and that too great an exoess of ferrio ohloride tends to retard the reaction. Series C. Test 1. Tne residue settles rapidly, leaving the solution oolourless. No visible hydrolysis. Dirty white semi-oolloidal preoipitata found to be largely sulphur. Test 2. Appreciable reduction to ferrous condition. The residue settles slowly. Series D. Test 1. Solution completely reduced to ferrous oiiloride. A small precipitate of sulphur on top of the settled residue. In Test 2 there was a fairly large precipitate of sulphur. Test3. The solution was only partially reduoed with small preoipitation of sulphur. Test 4 remained largely in the ferrio condition. Series E. Test 1. There was no visible hydrolysis and the solution was fairly reduoed to ferrous ohloride. Test 2 gave little reduction and consequently small preoipitation of sulphur. The general results of these series of experiments show that extraction is proportional to rise of temperature*, and that visible hydrolysis (i.e. preoipitation of ferrio hydroxide) is lessened as the concentration of ferrio chloride solution is inoreased. (2«r). The recovery of the sulphur from the residues was outside the obtjeot of this thesis. It nevertheless constitutes an important phase of this general problem. Two methods might be suggested as suitable for separating tiie sulphur from the residual gangue. The first is that of treating the residue with superheated steam, thus melting the sulphur whioh could be drawn off from the other material. The second method is that of employing some flotation scheme. From the nature of the residue the second method would seem to be the most advantageous. (See also page 40). No very marked difference in the percentage of extraction at 70 degrees C. and 60 degrees was observed. Consequently no further tests were run at 70 degrees. Having obtained these results and found that extraction inoreased with rise of- temperature, the remaining tests were made using quantities of ore and ferric chloride according to the amounts required for the chemical reaction. The ratio of ore to ferric ohloride was maintained oonstant; and by increasing this ratio with a constant volume of solution of 500 CC. the variation of the concentration of ferrio ohloride was made possible. This ratio was established as follows:- Per oent of iron in the ore 51.16 % Equation of reaotion:- 2 FeCl + Fe(S) = 5FeClp+(S). 324.4M- - 55.£4(Fe) 3S0.2S" (This assumes that the iron is all in the form of the monosulphide) _1 1 gram iron= .5116 = 1.95 grams of ore. 55.S4 gms. iron = 1.95 x 55.S4 — 109.1 gms. of ore. 324.44 Therefore 1 gram of ore requiras 109.1 = 2.97 grams of FeCl 3 The Ratloj ORE: FaCU = 1 : 2.97 9 (29). The concentrations are taken as grams of ferrio ohloride per litre. ( FOtf calculations see Appendix.) e.g. 10.0 grams of ore.— 29.7 gms.. FeCl. per litre* 5 To conform with the oapacity of the apparatus volumes of 500 CC. were used. A oharge was calculated on the above basis and the quantities halved, e.g. 5.0 gms.. of ore - -19.S5 gms. FeCl. per 500o*e. The object of the Series F,G,H & J was; to determine the effect of oonoentration on the extraction of iron from the ore at different temperatures. In eaoh series the temperature was constant. The time of each test was five hours. TABLE III. Series F. Volume of solution 500 CC. Temperature 60° C Speed of paddle 200 r.p.m. (approx.). Time of agitation 5 hours. Percent of iron In ore _5\\\6 fi___ Test. Weight of Cone, of FeCl, Increase In Percent^ of Percent of ore. in gms./ 500o.o. iron in gms. iron extracted, iron re duced to • • _—^____««» _ ferrous. 1- 7.5 23.25 3.65 94.7 # 98.2% 2.. 15.0 46.5 6.93 90.3 % 93.2 % *• 22*5 69.25 9.73 8h.5 % 88.6 % *+• 30.0 93.0 10.91 71.1 °J> 71.9 % 5- 37.5 116.25 10.4s 54.6 % 70.6 % <*• ^.0 139.5 9.S4 42.9 % 5S.0 fo Disoussion of Series F. 7/1 th low oonoentrations the amount of extraction of iron from (29a). VNUFACTURED BY. RENOUF PUBLISHING CO., MONTREAL O Ooyje^x^r O _/i/»X/*& O I * (30).. the ore is fairly large. It gradually falls as the oonoentration is increased. The reduction of the solution to ferrous chloride also falls. The percentage of reduction is in all cases greater than the extraction. This may be explained as being due to reduoing influences present in the small ore. AAamount of free HC1 acid ( Ifi to 2% is present. See p.24) present in the ferrio ohloride salt would oause a small evolution, of H S gas.- 2 This would accordingly causa reduction from ferrio to ferrous chloride. 2 FeClj 4 HgS = 2 FeCl2 *- 2 HC1 * S. Series G was run at £0° C under similar conditions to Series F. A slight errori was made in the oonoentration calculations for the proceeding experiments. This aooounts for the change of figures in the oonoentration column in the following tables. The tests of this series oovered a fairly wide field of concentrations. At the higher concentrations an exoessive frothing of the ore took place. In one case so much of the ore was bubbled cut of the bottle that the test had to be repeated. To obviate this frothing the agitation at the beginning of the run v/as made very small. The speed of the paddle was kept at about 50 r.p.m. for the first half hour and then gradually increased to the usual speed of about 200 r.p.m. A very small amount of frothing took plaoe with these precautions. Ta* little that did form gradually subsided altogether. The data relative to Series G follows on the next page in Table IV. TABLE IV. Series G. Temperature #0° C Time of agitation 5 hours. Iron in ore * 51.16 ft Volume of solution 500 o.o. (?1). Test. Weight of Cone of FeCl* Increase in Peroent of Percent ofL or a. in gms ./500 c. c. iron in gma.. iron extracted .iron reduoed . to ferrous. 1. 15 44.65 6.73 88.1% 96.5% 2.. 22.5 66.6*2 9.47 82.3 % 91.5% 3- 30.0 89.1 11.20 72.4 % 90.0 % 4. 37.5 U1.3ST 11.37 59*3 % #2.4 % 5. 45.X) 133.65 15.28 66.4 % £4.0 % 5e..(oheok) 45.0 133.65 15.59 67*7 fo 85*1 % 6. 52.5 155.98 21.26 81.1 % 79.1 % 1. 60.0 17S.2 19.59 63.S % 81.8 % The results of this series show a gradual deorease in extraction with increase of oonoentration until at a concentration of 133*65 gms./500 o.cr. the extraction rises. A maximum is reaohed at a concentration of 155.9& gms./500 o.o. ( see ourve). With further inorease of oonoentration the percentage of extraotion falls. This deviation from tne regular deorease was oheoked( test No. 5a), and approximately the same results were obtained. In general the e\;raotion is better at this 3temperatur to some e than at 60° C "he irregularity of the ourve may be due to si complexity in the FeClx aqueous solution. The next series, H, was run at 90° C Precautions were taken to prevent frathing by starting the paddles at a very slow sp^ed. The tendency for frothing to occur was at high temperatures and concentrations. The results of this series show a further inorease in the percental of extraction and reduction. No visible hydrolysis took plaoe in. the solutons during these runs. The rise;in the extraotion at a concentration of 1^.65 gms./500c.0. also ooourred in this series. But at the next highest oonoentration the extraotion begins to fall. (31a). MANUFACTURED BY. RENOUF PUBLISHING CO., MONTREAL 5 isoyja^/x^ ^ j^*^^ 3 * 8 (52). TABLE V. -u_. — _s_?IJLe_s A* Temperature — 90° C. Volume of solution - 500 o.o. Time of agitation — 5 hours. Speed of paddles 50 r.p.m. at start;increased to 200. Iron in ore 51.1.6 % Test. Ooao. ef FeCl* Weight of Inorease in Percent of Percent of iroa in gms./ 500o.o. ore. iron in gms. extraction, reduoed to ferrous. 1. 44.65 15.0 7.37 96.1 % 100 % 2. 6*9.1 50.0 11.94 77.7 % 99.5 % 4. 133.65 45.0 20.53 S9.2 % 99*8 % 5. 155.9S 52.5 22.09 82.3 % 97.6 % The experiments of Series J. were to obtain results at the highest possible working temperature. The usual precautions to prevent frothing were employed and the results obtained were very good. TABLE VI. Series J. Temperature 98° C. Other faotors and oondltlons the same as in Series H. Test. Cone, of FeCl. Weight of Inorease in Peroent of Peroent of iron in gms./500o.o. ore. Iron in gms. extraction, reduoed to ferrous. 1. 44.65 15 7.24 94.4 f> 98.9 % 2. 89.1 30 14.54 94.S % 91.9 % 3. 133.65 45 21.74 94.4 % 99.2 % The solutions were praotioally fully reduoed in each test to the ferrous condition. The percentage of extraction was high and was approximately the same fer each oonoentration. The ourve of extraotion is almost a straight line as plotted from the above figures. (32a). MANUFACTURED BY. RENOUF PUBLISHING CO., MONTREAL 5r SJ si 3 \K :»: H\ ^ 'MSt; ^ v % ^ s hs J;ii I <3 5 5 1 XT I i? ~ -• r * * r:x _L_ o l{o/foas/*j? u ^/ * ****/ § « (32b). MANUFACTURED BY. RENOUF PUBLISHING CO., MONTREAL I « Q a § (33). There was no visible hydrolysis, and the solutions were bright green in oolour and perfeotly clear after the residues had settled. The precipitate of sulphur and the sludge was black in oolour and floccuient in character. The settling was much more rapid than in any of the preoeeding series ef experiments. The following table is compiled from the results in Tables III, IV, V, & VI. The ourve shews graphically the effect ef temperature on the extraction at definite concentrations. TABLE VII. Temperature. Peroent of Iron Extraoted frem Ore. Cono. FeCl?. 44.65gms./5QQoo. g9.1g/500oo* 133.65g/50Qee. 60° C 90.3 % 71.1 % 42.9 % 80° 0. 88.1 % 72.4 % 66.4 % 90° C 96.1 % 11.1 % 89.2 % 98° C. 94.4 % 94*ff % 94.4 % The ourve shows that as the temperature rises the effeot of concentration en the extraotion diminishes. At 95° C. the percentage ef iron extraoted from the ore is practically the same for eaoh concentration. The curves of reduction with oonoentration shew a general tenuenoy to become horizontal as the temperature rises. The oonolusions drawn from these aeries of experiments shew that the eptimum temperature for the maximum extraotion is 98° C. In general concentrations 133.65 gms. FeCl, and 155.VS gms. per 500 o.o. give the best working results. The next experiments were to determine the rate ef reduction of the leaoh. In Test He. 1 25 % under the theoretical quantity ef ere was used. This gave an exoess of ferrio chloride solution. In Test No. 2 the ore was 25 % in exoess. The concentration of the ferrio ohloride solution in (?3a,). ANUFACTURED BY. RENOUF PUBLISHING CO., MONTREAL Qvfjy^^yxj? £ V^"-"^^ ! £ « (33b). MANUFACTURED BY. RENOUF PUBLISHING CO., MONTREAL § -Ijoyonpag, £ JUs^e^ * £ § (34). Test 1. was 89.1 gms. per 500 o.o., for whioh the ore should be 30 grams. The oonoentration of Test 2. was 111.38 gms. per 500 o.o*, the ore for which should theoretically be 37*5 grams. The temperature of the run was 60° C. Every hour a one o.o. sample was pipetted from the bottles and analysed for iron( ferrous ). The agitation was stopped after eight hours morning and the leach allowed to stand over night. In the a sample was taken out A and analysed, and the agitation oontinued for another seven hours.The results are recorded in grams of ferrous iron In the total leach. TABLE VIII. Series K. Hate of Reduction Experiments. TEST No.l. Weight of ore ~ ZH.5 gms. TEST No.2. Weight of ore — 45 gms Iron in ore 11.51 gtn*. Iron in ore —23.02 gms. Cone, of Sol.-S9.1 gms./500o.o. Cono. - 111.3£gms./5QQco. Fe content- 30.64 gms. Fe content — 36*.22 gms. Time in hours. Ferrous Fe in Time in hours. Ferrous Fe in total solution In gms. e total sol. In gms. 1. • 19.1 1. zs.o 2. Z50 z. ^.6 3. • 27.5 3 37.3 4. • - 29.4 4 39.5 5. • 2:9.4 5 fl.O 6. ^0.2 6 - 11.3 7. • 30.3 7. ifcj.ff 6*. W.5 8. • 30.6* Standing over night. 0. Standing over ni»jht 0. — 4jf.H 1. 32.0 1. <*if d. 32.0 #0 2 45.0 3. 32. u 3. - 45*0 «*. _)H.Z 5. u. a . 32.4 6 0 6. 5. if 0 - 32^r 6# 6 - %.2 • 3'd.88 Total iron at end of run— 39.72 om. Total Iron at end of run — 51.55 gms Inorease in iron 9.09 gms. Inorease in iron 1304 gms. Peroent of extraotion 79.0 fo Peroent of extraction $8 % Percent of reduction 6*2.6* % Pereent of reduction #9.3 % (34a). MANUFACTURED BY, RENOUF PUBLISHING CO., MONTREAL l V > 8 ^ Swtu£ o/ ^ Z/ The results of these experiments are plotted on a time base. The ourve shows that the relative rates of reduotion for each test are very similar. During the first five hours the most appreciable reduetion takes place. The ourve of Test 2 shows greater reduction, this being due to the excess of ore present. To determine the effect of adding fresh ferrio ohloride solution to a partially extraoted residue of ore, two tests were oarried out (SeriesL Test No*1 used 50 % under the theoretical amount of ore with 500 o.e. of ferric chloride solution. It was agitated at 60 C. for eight hours. A five o.o. Bample was removed for analysis, and after standing over night , it was again agitated for another eight hours. Teet No. 2 used the theoretical amount of ore with 500 o.o. of ferrie chloride solution. It was agitated for eight hours , after whioh a sample was removed and analysed. The residue was allowed to settle during the night. The following day the supernatent liquid was siphoned off and the residue filtered. 500 o.o. of fresh ferrio ohloride solution of the same oonoentration was added to this residue and further agitated for eight hours. A thin film of gasoline was used on the surface of the solutions to exoiude air and prevent oxidation of the leaoh. CALULATIQiaS FOR SERIES L. lgram ore requires 2.97 gms. FeCl* 20 gms. ore require 59.4 •' " Test No.l 10 gms. ore 59.4 gms./ lOOOcc. FeCl. Test Ho.2 2o gms. ore 59.4 gms./ lOOOe.o. " Fresh solution 59*4 gms./ lOOOo.o. " (36). TABLE IX. Series L. __ Test No.l Test Ncjg Wt. of ore 10 gms. — 5*116 gms. Fe...... 20 gms. 10.23 gms. F Cono. FeCl} sol. 59.4 gms.//0OQoc...... 59.4 gms./#00oo. Temperature 60° C ...... 60°C. 1st. DAY. 2nd. DAY* 1st* DAY. 2nd. DAY. Increase in iron — 4*,46* gms. 0 ...... 7.99 gms. 0*1& gms. Percent extraotion - 81.5 % 0 % ...... 18.1 % 1+1 % Total percent extraotion 81.5 % • 79.6*^ The results of these experiments show that with an exoess of of FeCl. solution the maximum extraotion is obtained during the first eight hours. In the two stage leach a very small amount of iron is extraoted in the seoond agitation. These teste oonfirm the results of the previous series in whioh it was found that- the maximum extraction takes place during the first five to eight hours of leaohing. The two stage operation would necessarily ba employed in a works praetice. For electrolysis a fully reduoed solution is required. A fresh solution of ferrio ohloride would be agitated with partially extracted ore. This operation would remove the last of the Iron. This solution, now partly ferrous and partly ferric ohloride, would be agitated with an excess of fresh ore and fully reduoed to ferrous chloride.. The combined operation is a cyclic one. The gasoline film on the surface of the solution had no very appreciable effect on the results. If any it might be deleterious in that it would form a film on any ore petioles coming in oontaet with it, and (37). thus preventing the FeCl^ from acting upon them. An experiment was carried out to determine the rate of extraction. A 45 gram sample of ore with 500 ec. of FeCl^ solution of cone. 133*65 gros:* per 500 ee.was used. The temperature was at 6*0° C and the agitation extended over a period of seven hours. Every hour about five o.o. was taken from the bottle and filtered. A one o.o. sample was pipetted from the filtrate, reduoed with zinc and analysed for iron. Tha remainder of the filtrate and the filter paper and residue were returned to the leach. The liability for error was large and the results obtained were not very satisfactory. But a relative idea of the rate of extraetion was obtained. Sufficient points were found to plot a ourve on a time base. TABLE X*. Series M. Rate of Extraotion. Temperature £0° C. Weight of ore 45 gms. « 23.05 gms. Fe. Cone, of leaohing sol. — 153*65 g*a** FeC^? /50° 00. TIME IN HOURS. PERCENT OF TOTAL EXTRACTION. 0 0 % 1 18 % 2 21..9 % 3 27.9 % 4 — 5 6 44.3 % 1 44.3 % h Blanks are were the results showed a deorease in extraction. A This was due to an error in sampling. The results are much lower than those of a continuous run. But the test further confirms the previous results, showing that the reaotlon takes plaoe during the first five or six hours. (37a). NUFACTURED BY. RENOUF PUBLISHING CO., MONTREAL (38). All of the proceeding experiments were made without any additions of acid to the leaohing solutions. To determine what effeot small quantities of acid would have on the leaohing, a series (N) of testa were oarried out. A 30 gram sample of ore with ferrio chloride solution of 6*9*1 gms./500 ec. concentration was used. Increasing amounts of concentrated hydrochloric acid were added in each test. The temperature of the leach was 80° 0. TABLE XI. Series N. Effect of Additions of HC1. Temperature 80° C*. Time of leach 5 hours.. Weight of ore 50 gms. -- 15.35 gms. Fe.. Cone, of leach 89.1 gms. FeCl3/500 oe*. Aold HC1. Sp.Qr. 1.19 0*JV Test Ho. HC1 added. Percent by vol. Pereent extraotion. Percent reduce? 1* 10 oo. 2 % 62.7 % 88.1.% 2. 20 so. 4 % 64.0 % 90.6 % 5* 30 oo. 6 % 64.6 % #4.2 % 4. 40 oo. 8 % 64.0 % 6*7.0 % 5* 50 oo. 10 % 100 % 100 % The results of these tests show no acceleration In the extraction of Iron from the ore until 10 % has been added. In this oase 100 % of the iron goes into solution. On removal from the bath the solution was blue green In colour and the precipitate was blaok and floeculent. There was a strong evolution of E,S gas. When Test No. 4 was removed from the bath, the sludge settled rapidly leaving a clear orange green solution. There was no appreciable evolution of %S. After standing for a short time a reaction began and <59). H2S is vigorously evolved. To offer an explanation for this action, is somewhat difficult. It may be due to the precipitating sulphur coating the ore particles and thus preventing their coming in contact with the HC1. As the solution cools this film or coating of sulphur cracks or breaks away thus allowing the action with the acid to take place. After standing for several days the solution separated into two distinct layers*, a odourless liquid on the bottom and a bright green on top. On examination it was found that the colourless liquid was saturated with hydrogen sulphide, while the green solution above gave no odor of the gas. Apparently the addition of less than 10 % of add has very little effect on increasing the amount of extraction of iron from the ore. Ten percent or over greatly increases the efficiency of the leaohing solution. But it introduces complications and produoes conditions which are unfavorable for electrolysis. There is the evolution of H^S gas. This means the loss of. part of the sulphur as a by-product. The solution which should be kept with as low a hydrogen concentration as possible becomes acidio. Thus it olearly shows that while the addition of acid may Inorease the extracting power of the leaohing solution, the disadvantages brought about by its use considerably outweigh its advantages. This completes the experimental work on leeching. The general results show that the optimum temperature for leaohing is 96*° C. Low concentrations of ferric ohloride give better extraction results. But for working conditions solutions very high in iron are necessary. At 98° C* the extraction was practically the same for all concentrations* The precipitation of ferrio hydroxide, due to hydrolysis, does not take place in highly concentrated solutions even at the highest temperatures at whieh the tests were oarried out. Practically all the extraotion is (40). completed during the first five hours of the leach* In that period 96 % of the iron in the ore was brought into solution. SULPHUR. In the previous pages mention has been made of the sulphur which is precipitated during the leaohing reaction. Its recovery in a pure state constitutes a somewhat difficult problem. The sludge from a leach contains all the gangue lnthe ore, consisting of silloa, alumina, etc., and a small amount of undissolved sulphide. The suggestion has already been made that a flotation scheme offers the beet solution for recovering the sulphur from this residue. An attempt was made to see if the sulphur,if mixed with boiling water, would float. But the results were not satisfactory. Tha sulphur after settling from the initial agitation apparently loses its floeculent character and settles along with the other constituents when it is re-agitated. The separation would be more effective if oarried out in a flotation maohine. In the writer's opinion no attempt should be made to recover the sulphur as a pure produot. The entire residue as recovered from the filter presses should be used for the manufacture of sulphurio acid or 802 gas for sulphite treatment of wood pulp. The only treatment necessary would be the thorough washing ef the filter oake and drying. In this condition it could be shipped to sulphuric acid plants or pulp mills, or used for sulphuric aoid production on the spot. This appears to be the most advantageous method of utilizing the sulphur as a by-product. Fer every ten of iron extraoted from the ore the yield of sulphur is theoretically 1140 lbs. (41). COPPER. From the analysis of the ore it was found that the amount of copper present was 1.5© %* Aocording to the reaotions, as given under the theoretical discussion of leaching, the oopper sulphide is also soluble in ferrio ohloride. A number of analyses were accordingly made on the solutions obtained from leaohing to determine the amount of oopper dissolved from the ore. The results were negative. But on analysing one of the residues only 0.1 % Cu. was found. From these conflicting results, it is difficult to draw a conclusion. The amount of copper is in all oases very small, while the iron is in a very large excess. This interferes in the ordinary methods of analysis. From the analysis of the residue it would be safe to assume that the copper does go into solution. There was not sufficient time to carry out further investigations and determine the amount of oopper dissolved at the different temperatures and eonoentratlons. Copper will be a very valuable by-product of this prooess. Its recovery from the ferrous chloride solution does not present a very serious problem. As has been already mentioned it oan easily be recovered by passing the solution over scrap iron or preferably sponge iron. The zino in the ore was only a little over a half a per oent. No attempt was aade to determine its presence in the resulting leaoh. The working out of methods of separation and recovery of the by-products of this process constitute a large field of research and experimenting. (42). To obtain sufficient ferrous ohloride solution for electrolysis a leaching apparatus of larger capacity was constructed. A large exoess of ore was used in order that the solution should be fully reduoed to the ferrous condition. The runs were in no sense experimental, but solely to obtain a large volume of solution. The charges and calculations have been recorded and the results are given as showing the effect of leaohing with larger volumes than in the proceeding tests. The possible percentage of extraotion is calculated to serve as a comparison with the tests using the theoretical quantities of ore and ferric ohloride. A diagram of the apparatus Is shown in Fig.2, Plate No.l. A large galvanized iron pail (a) was used as a water bath. The leaohing was carried out in an earthenware jar (b) of three gallons capacity. A wooden paddle (c) caused the agitation, being driven by a pulley (d) connected by a belt to a small 1/6 H.P. motor (g). The bath was supported on bricks (1) and the heat supplied by a Ueker burner (h). A ring stand (f) served as a support for the paddle shaft. This shaft ran in a bearing through a wooden oover (e) on top of the jar. A number of runs were made , of whioh the following are typical. (43). RUN 1~X CHARGE: 1000 gms*. ore (511.6 gms. Fe.) 8 litres leaching solution of cone. 106.06 gms., Fe/litre. (69.77 gms. ferrio Fe/litre) (32.29 gms. ferrous Fe/litre). Time of agitation 4 hours. Temperature of water bath — £0°C. Excess of ore used. RESULTS: Solution completely reduoed to ferrouB chloride. Total iron In final leach 1116.4 gms. Iron in initial solution g4g.4 ^ms. Inorease in iron 26£.0 gms. £££ x ioo _ Percentage extraotion —511.6 *- 52 % N.B. The ferrous ohloride in the initial leaohing solution was from the waste solution collected from all the previous experiments. RUN 2-X CHARGE CALCULATIONS. Concentration of leaohing solution 117.4lgms- Fe/litre (340.4£gms. FeCiyiitre.) From Ratio: 1 litre requires 114.6 gms of ore. 9 litres require 1031.4 gms. " " Excess of 289 gms. of ore added. CHARQE: 1320 grams ore. ( Fe content 675*^1 gms. ) 9 litres FeCl* solution. Time of run 4.5 hours. Temp, of water bath — 95° C. (about). (44).. RESULTS: Solution completely reduoed to ferrous ohloride. Concentration of resultant leach — 170.64 gms. Fe/litre. Total iron in final leaoh 1535.76 gms. Iron in initial solution 1056.69 gms. Increase in iron — 479.07 gms.. Percent extraotion 71 % Percent of possible extraction 90.8% The percent- of possible extraetion is calculated from the theoretical quantity of ore and not the exoess. RUN 3-X CHARGE CALCULATIONS: 9 litres of FeCl^ sol. Cone. 102.56 gms. Fe/litre 297.42 gms FeCiyiitre. Ore required 100 gms. per litre Exoess ore 200 gms. Total charge 1100 gms. of ore. (Fe— 562.£6gms.) Time of run 5 hours. Temp, of water bath — 95°C. (about). RESULTS: Solution completely reduoed to ferrous ohloride. Concentration of resultant leaoh 145.27 gms.Fe/litre Total iron in final leaoh 1307.43 gms. Iron in initial solution 923*04 gms. Iron extraoted 3#4.39 gma. Percent extraotion 66V4 % Peroent of possible extraction #3*6 % The solution obtained from these runs was used In the experiments on the eleotro-depositlon of iron. (45). C. Electro-deposition Experiments.* Tha experimental work,oonneoted with depositing iron from the solutions of ferrous ohloride obtained: by leaching pyrrhotita ore with ferrio ohloride solution, comes under three headings. I. Large eleotrolytlo cell with diaphragm. II. 8mall electrolytic oell with diaphragm. III. Small oell with soluble anodes and no diaphragm. I. Experiments with Large Cell Fig*5# Plate No.2 shows a plan of this oell.A sectional view is shown in Fig. 3a, Plate Ho. 3. On Plate No.4 several of the details of the eell are shown. The design was based on the type of cell used at Milford, Conn, by F*A.Eustis, and at Trail, B.C.. by the Consolidated Mining and Smelting Co* Ltd. The oell was of wooden construction with inside dimensions of 9 in. x 9 in. x 6* la. A layer of neat cement in the bottom reduced the depth to 5f in. Stay bolts (k) kept the sides rigid.The cylindrical oathode (a) rotated horizontally in two bearings, one (n) in the side of the oell, the other (g) whioh could be removed on. the opposite side. The cathode was a pieoe of iron pipe 5 1/16 inehes long and 2 15/16 inches in diameter and polished very smooth. The surface area (not including the ends) was approximately 0.J5 sq.ft.- It was supported by shafting at each end of 2 in. and 10 7/16 ia. In length respectively (Fig.5 Plate No.4). The longer end ran ia a brass bearing (p) set in the removable side (Flg.6) already mentioned. It consisted of a pieoe of planed 1 5/16* board 5 la* x 6 la., in which was sunk a brass bearing (p) held by bolts to a face plate on the outside. A rubber gasket made a tight fit against the side of the eell, in whioh there was an opening the width of the brass bearing.- The board was held tightly against the side of the oell by long wood screws. The electrical contact to the cathode was made by a oopper PLATE NO. 2. f^/a/i of E/ectro/y/iC Ce// for /ro/j Deposition. One Third flcrva/ J/ze. -6" Immal F/g J. KffM'C t-A-2$ PLA T£ NO. J. DM\ra//6n of E/ec/ro/ytic Ce// a/ony Section *-* Eio.d. f/f. J A. WR.Mt S-4-J.i- FOLATE No.4. flnode / Thick. P/an of //node One Third Ac fat*/ /ok SmtStrttM ' \^m ^Wil^l E/an ofCa/AoJe O/re Third /fcr R»iber G + The anodes (b) also (Fig.,4, Plate No. 4) were graphite slabs 1 la. thick and 5 1 in. x)i in. Quarter inch iron rods were threaded into the graphite. Strips of hard wood (d), through whioh the iron rods fitted tightly, supported the anodes in the cell. Eleetrical oontaet was made to the iron rods by screw connections. The asbestos cloth diaphragm (g), making the cathode eompartment, wai held between two thin pieces of wood(c) and fitted closely around a wooden frame (e) Fig.3 & 3a., at each side of the cell. An outlet pipe (J ) at the bottom of the cell allowed for a flow of solution from the anode compartment. The fresh solution flowed Into the cathode compartment by a glass tube from a coil immersed in a water bath. The cement layer (m) prevented leaking at the Joints. The ferrous ohloride was stored in a large jar above the level of the cell.. It flowed by gravity through a glass coil which was immersed in a water bath kept at 100° C. A flat pieoe of cork (f) fitted oloaely against the adjustlble bearing, keeping the electrolyte from coming in contact with the brass. Fig.7, Plate No. 5 shows the electrioal connections.- A motor generator set consisting of a 4 H..P., D.-C. motor and a 10 volt D.C. generator supplied the energy for the eleotrolysls. A large coil resistance in series reduoed the e.m.f.. to the required figure. No coating was used on the cathode. The surfaoe was thoroughly cleaned and polished. The ends of the oathode and the shafting were shellaced in order to prevent deposition on those portions. PLATE NO. 5. F?f. 7. //oroits\ irfrincj Diagram Large Ceii. f/j.G 4V/>iny D/a^rar/x 6ma// Cei/ F/'f-G. riotor P- puses . Generaior S* Snitch Start in q So A ffnim e t e-r~ « %*S'S f«f?ee. • Ban4c o/lonrA /resistance Co// r* r^oferf r/ o met e/~. \to/tn?e-t tV-f-M^L. S (47). RUN __NQ* 1. This was a trial run to ascertain the working conditions of the eell. The details of the test are as follows:- Conoentration of electrolyte 165.4 gms. Fe/litre. Speed of mandrel }88 r.p.m. Current density 57 amperes/sq. ft. Voltage - - 4.0 to 4.2 volts. Temperature of electrolyte at start 53° C. The results proved that the heating arrangements were un satisfactory. In this case the solution flowed through a Wolff bottle immersed in a water bath. It was Impossible to obtain a temperature over 50° C. At the beginning of the run the oathode was not completely immersed in the electrolyte, It was found that the oirouit efficiency was better when the oathode was fully covered by the solution. The run lasted about two and a half hours. A black sludge formed on the depositing surface. The deposit of iron was poor. It was roughs gray in colour, but free from. holes or pits. The oonoentration of the solution after the run was 138 gms. Fe/litre. The heating arrangements were now changed. A glass coil was placed in a round water-tight tin, standing on a tripod. The solution entered the ooil at the top from the large supply jar. The bottom of the ooil passed through a cork whioh was fitted into an opening soldered to the side of the tin near the bottom. The tin was filled with water and kept boiling by a Meker burner. RUN NO* Z. Oonoentration of electrolyte 153 gms. Fe/litre. Speed of mandrel 4£0 r.p.m.. Current density 57 amperes/sq. ft. Voltage - - 3.0 to 3*4 Volts. Temperature of electrolyte at start — 59° C Time of run - 8 Hours. Flow of electrolyte through oell — About 2 litres per hour. It was not possible to get the temperature of the electrolyte ia the oell over 50° C. even with the changes made in the heating apparatus. After running for five hours, the solution was circulated, the anolyte solution being added to the supply Jar and thenoe flowing fairly quickly through the coil to the oathode compartment. In this way the temperature of the electrolyte in the oell was brought up to 73° C- The deposit was email in amount, dark gray in colour and ribbed, but not pitted* It was fine grained* At the edges of the cathode the deposit was clndery* A considerable amount of oxide was Included in the deposit* The diaphragm was heavily impregnated with iron oxide.. The addition of ferrio ohloride to the catholyte, by circulating the electrolyte, had a deleterious effect on the deposition. A chemical analysis of a small sample of the deposit analysed over 99 % iron. On the whole the run was not a success as far as the deposit was conoerned. But some important Information was obtained whioh is summed up in the following oondiderations. No ferrio ohloride should be in the oathode compartment. The temperature of the eleotrolyte should be over 75° C*. The oathode should be totally immersed In the electrolyte. Tha heating of the solution should be in the oell • (49).. On account of the difficulties involved regarding the heating of tha electrolyte and the large volume necessary, It was deeided to eonstruot a much smaller type of cell* For any effective heating in the large oell it la neoeasarjr to have either steam coils or A.C. eleotrical resistancee immersed in the electrolyte itself. II. Experiments with Small Cell. *•* ^ '11 - • i i 11—•—m§—• • • j ..i i j i m m. ^ • L The coll consisted of a lOOOeo. Pyrexbeaker, divided into two compartments by a cylindrical asbestos diaphragm. The oathode was a piece of steel rod machined to -f in. in diameter and 2 ia* long, into whioh was threaded a -J- ia. shafting to support it in the cell. In this case the oathode rotated vert1tally. The effective surface area of the mandrel was 4.J1 eq. in. .0327 sq. ft. — .0966* sq. dom. ( This does not Include the ends). The anodes were at first graphite strips 4£ in. long, 1 in. wide* and •£- in. thick, supported in wooden frames and having screw connections threaded into the top. Later carbon anodes were used. They were cut from a hollow carbon oyUnder, and further cut iato two pieces parallel to the vertical axis. The dimensions were as follows: length, 5 in. , diameter 4 in.-, thickness -£• in. The soluble anode used in the final experiments was a pieoe of sheet iron fitting around the Inside wall of the beaker. The diaphragm was 5 in. in length and about 2 in. In diameter. It was made of two layers of high grade asbestos eioth fitted around a one inch wooden block at the bottom and a wire frame at the top. The ends of the wire frame extended over the edges of the cell and held it seourely in the oentre ef the beaker. The cathode was driven by a flexible shaft from a small adjustible speed motor. But later a belt. drive was found to be more efficient. The oell was at first used in a water bath to furnish the (50).. heat. But thie did not prove very satisfactory; so direct heating was employed, the oell being jacketed with an asbestos covering. Fig.9> Plate 6, shows a diagrammatic outlay of the apparatus. a. Cell (pyrex beaker)., b.o. Bearing and chuck for holding cathode. d. Bearing to steady oathode shaft. e. Thermometer. f. Anode. g. Inlet tube from supply tank to oathode oompartment. h. Outlet tube from anode oompartment. i. Supply tank (glass bottle). k. Bottle for oolleoting solution from anode oompartment. 1. Coupler connection for leads to eleotrioal supply. m. Motor for rotating cathode. n. Belt. p. Leads to eleotrioal supply. q. Leads to voltmeter. r. Tap to regulate flow of solution entering cell. B. Ueker burner. t- Pinch cook to regulate the flow of aaalyte from the cell.. Fig.S, Plate No.5, shows the wiring diagram of the eleotrioal connections. The ourrent was taken from the lighting oiroultr at 110 volts. It passed through a lamp bank resistance in series and a small rheostat connected as a potentiometer. The potentiometer connection was after a time discarded, and good oontrol was obtained by using two 8 C.P. carbon Umps along with two 16 C.P. and eight 32 C.P.- carbon lamps in the lamp bank. The small motor was operated from the 110 volt supply. The voltage. across the eleotrodes was reoorded by a five volt range Weston voltmeter. (50a). Photograph of Small Electrolytic Cell and the general equipment oonnectod with it. It is shown without th© water bath. (51)* The ourrent was read from a 25 ampere range ammeter. Tne factors involved in the electro-deposition of iron are numerous. Among the most Important may be mentioned:- 1.- Concentration of electrolyte. 2.. Current density and voltage. 3. Temperature of electrolyte* 4.. Speed of rotating cathode. 5. Time of electrolysis. 6. Nature of. oell.(With or without diaphragm.) 7* Nature of anode. (Soluble or insoluble.) Time did not permit for the investigation of all these factors in relation. to each other. But a number of combinations were made, the results of which are recorded from the following experiments*. SERIES A. These were trial experiments to determine the working conditions of the oell. RUN IA. Concentration of electrolyte 162.5 gms.Fe/litre. Temp.. 6*4.ff° C. CD. — 6*9aiap8./sq.ft. Voltage 2.45 volts. Time of run 1.5 hours. No flow of solution through oell. Diaphragm used and graphite anodes. Thin film of powdered graphite and oil on cathode. Speed of oathode, 500r.p.m. An analysis of the oatholyte during the run showed a steady inorease in oonoentration. This was probably due to evaporation. The deposit was soft and pitted and nodular at the bottom. The graphite coating was not very satisfactory. The deposit weighed 2.61 grams, thus giving a ourrent efficiency of only 59 %. ( Theoretical deposition 4.45 gms.) (52). RUN 2A. The concentration of the electrolyte was the same as in the previous run. A small flow of solution was maintained to keep tha elec trolyte at constant level. Average CD. — 60.6 amps./sq.ft. Average voltage — 1.6*6volts. Temp. — 75°C Time of nun 2 2/3 hours. Speed of oathode 500 r.p.m. A few drops of glue were added to the catholyte fifteen minutes after starting.. The hydrogen liberated at the oathode was observed collecting in the supply tube leading Into the oathode compart meat. The deposit was fair; gray in colour, except towards the bottom where It was quite white, smooth and coherent. But it was soft on the central part of the mandrel. Considerable oxide of iron was included in the deposit. The next three runs of this series were with a dilute solution. No diaphragm was used and thoy were oarried out at room temperature( 17°C). of The time eaoh run was for fifteen minutes. The object was to determine the A effect of the speed of the oathode on the nature of the deposit. RUM 3A. Current density — 60 to 90 amps./sq.ft. Voltage 2 volts. Cathode stationary. The deposit was silver white, but flaky. It did not adhere to the oathode, but curled off In thin Bheets or scales. RUN 4A. The same solution as in Run J. was used. The conditions were the same exoept that the cathode was rotated slowly,(about 50 r.p.m.). The deposit was similar to the above, but not as scaly. It was very brittle. (55). RUN 5A. The same solution and conditions as above, but the cathode was rotated at high epeed( 1£00 r.p.m.). The deposit was silver white, coherent and; smooth, and adhering olosely to the depositing surface. From these tests it was infered that high speed rotation of the cathode made for a smoother and more coherent deposit. The oell worked satisfactorily in regard to its meohanioal and physical characteristics. Temperature, current density, flow of electrolyte and speed of oathode could be olosely oontrolled. SERIES B. These experiments were made with the object of determining the effeot of temperature, speed of cathode and concentration of eleotro- de./oos/t lyte on the resultant of iron. The first four tests were made without A using the diaphragm. The rest of this series were run with the asbestos diaphragm. In the first half of the series the graphite anodes were used, in the remainder the circular oarbon anodes were used. The circular anodes reduoed the resistance of the cell. Readings of ourrent, voltage and temperature were taken every ten or. fifteen minutes. The figures given below are the average during a run. RUN IB. Concentration of electrolyte — 162.5 gms.Fe/litre. CD. — 91 amps./sq.ft. Voltage 2.4 volts. Speed of oathode 1000 r.p.m. Temp. —- 16°C Time of run — 1 hour. Volume of electrolyte — 1 litre. The deposit was very poor. Blaok sludge formed on the oathode. It was very soaly and thrown off from the rotating cathode. (54). RUN 2B. Concentration of electrolyte 157.25 gms.Fe/litre. CD. 91 amps./sq.ft. Voltage 2.51 volts. Speed of cathode — 250 r.p.m. Temp. — 20°C Tima — 1 hour. ( Difference of potential across electrodes, current off, 0.9 volts. ) The deposit was metallio, but poor. It was scaly and adhered badly to the oathode. RUN 3B. Concentration of electrolyte 162.5 gms.Fe/litre. CD. 91 amps./sq.ft. Voltage 2.0 volts. 8peed of oathode 250 r.p.m. Temp.— 6l*3°C Time — 1 hr. The electrolyte soon became very murky and yellow. The deposit was very poor and considerable sludge formed on the cathode. RUN 4B. Concentration of electrolyte 81+3 gms*Fe/litre* CD. 91 amps./sq.ft. Voltage 2.57 volts. Speed of oathode — 200 r.p.m. Temp. — 62°C Time— 1 hr. Visible hydrolysis of the electrolyte is very soon apparent. At the surface of the cathode , the deposit was white and metallio. But this metallio deposit was thiokly ooated with black sludge. This was found to be magnetio, and is no doubt largely composed of finely divided iron. The results of these four experiments show rather conclusively that the presence of ferrio oaloride in the solution around the cathode affects in an adverse manner the nature of the depositing iron. This confirms the results of a similar condition in the large oell. The remaining six tests of this series were run with the diaphragm, constituting a two oompartment oell. The description and results (55). of eaoh tost will follow in detail. RUNJ5B. Concentration of electrolyte — 155 gms.Fe/litre. CD. 91 amps./sq.ft. Voltage 2*4 volts. Speed of oathode 250 r.p.m. Temp. -- 75°C Time — 2 hrs.- The water bath was used. The flow of eleotrolyte through the oell was about 1 litre/hour. The flow was started ten minutes after the beginning of the run. A few drops of glue were added to the catholyte during the run. The deposit was fair; hard, gray in oolour but slightly pitted. It was quite bright and coherent on the cathode surface. There was no sludgy iron on the deposit. The weight of the deposit was 5»80 grams, giving a current efficiency of 95%' In the remainder of the tests the graphite anodes were replaced by the circular carbon plates. RUN 6B. The concentration of the eleotrolyte was the same as in the proceeding run. The ourrent density was increased to 151.5 amps./sq.ft. The temperature was raised to #5°C>and the speed slightly increased to about 300 r.p.m. The voltage was 2.6* volts and the time of the run 1-J- hours. The other conditions were similar to the above. The deposit was very poor. It was rough and nodular and was covered with considerable black sludgy iron. Underlying the rough exterior was a very thin white metallic deposit. RUN 7B. In this test the speed of the oathode was increased to 1000 r.p.m. in order to discover what bearing this faotor would have on the nature of the deposit. Oonoentration of eleotrolyte 152 gms.Fe/lltre. CD. — 154.5 amps./sq.ft. Voltage 2.7 volts. Temp 83°C. Time of run " X hour* (56). The deposit was fair, much smoother than the previous one and had no outgrowths. The thickness of 1/6*4 in. was even over the entire surface. It was somewhat porous, brittle and still had a coating of blaok sludge. The under surface was white. RUN SB. From the results ef the previous run it was decided to further increase the speed of the cathode. Concentration of eleotrolyte 152 gms.Fe/litre. CD. 154.6* amps./sq.ft. Voltage 3*15 volts* Speed of oathode — 1600 r.p.m. Temp.— £5°C, Time — 5 hrs*. Direct heating of the oell was substituted for the water bath* The flow was a little under a litre /. hour* Before the run the oathode was piokled in a solution of 1:1 HC1 for a few seconds, and then well rinsed with distilled water. The deposit was good, about 1/32 in. thick, gray in oolour, slightly rough on tha surface and easily removed from the oathode. There was considerable treeing at the bottom. The weight of the deposit was 16.-0 grams, giving a ourrent efficiency of 6*5*5 %• A small specimen of the deposit was annealed in magnesia ( to reduce tendency to oxidize) at a bright red heat (about 900°Cv) for fifteen minutes. It was quite malleable and could be bent 90 degrees without fracture. Several samples were imbedded in Wood's metal(M.P.. 60°C.) and polished. When examined under the microscope they were seen to be- very porous. The solid struoture was typioal of pure iron, ferrite, but the porosity was shown by a large number of black spots and points. Whether this porosity is due to gas holes or included oxide it was Impossible to determine. (57)* RUN 9B. Concentration of eleotrolyte 152 gms. Fe/litre. CD. 206 amps./sq.ft. Voltage 3.15 volts. Speed of oathode — 1800 r.p.m. Temp. - 94°C Time — 5i hours. The oathode was pickled previous to the run with 1:1 HCl. The evolution of gas at the oathode was quite large. The flow of solution was from J- to -f litres/hour. The deposit was poor. It was rough and nodular*,the nodules running vertically along the oathode. The oolour of the deposit was dark gray and there was considerable treeing at the top and bottom of the cathode* The ourrent density was probably too high* RUN 1QB. This was the last run of this series. The belt drivo was substituted for the flexible shaft and better speed control was obtained. Oonoentration of eleotrolyte 157 gms./litre of Fe. CD. 192.4 amps./sq.ft. Voltage 2.4# volts. Speed of oathode — 1400 r.p.m. Temp. - £5°C Time - 5 hours. The oathode was pickled as in the preoeeding runs. The flow of solution was about 1 litre per hour. The deposit was fair. It was 1/16 in. thick, gray in oolour, but rough and porous. There was large treeing at the base.. After annealing (at about 900°C ) it was only slightly malleable. Thi* was probably due to its porous struoture. A specimen was imbedded in Wood's metal and polished for miorosoope analysis. The flat surface of the specimen was examined. The photograph shows very olearly the extremely porous nature of the iron. No doubt a great deal of this porosity oould be reduoed by rolling, for it is probably largely due to occluded hyrogen. Two micro-photographs are shown on the following page. (57a). jr Etched specimens photographed under high power magnification. The extreme porosity is very marked. The white is pure iron (ferrite). The specimens are from deposit 10 B. (58). The positive results of this series were not on the whole satisfactory. But at the same time considerable information was obtained whioh enables one to formulate the conditions under whioh good deposits should be obtained. The following deductions are based on the results of the foregoing experiments. The concentration of the eleotrolyte should be high, so that the available iron ions at the oathode surface be large. A diaphragm is necessary and the oatholyte should be entirely in the ferrous condition. The flow to maintain this condition- will vary with the size of the oell. The current density should be high*: about ISO amperes per sq. ft. seems to be the optimum. The voltage should be kept low. The temperature of the eleotrolyte should be from #0°C to 90°C The speed of the mandrel is governed by its size. In the case of the small oell tests, the beat deposits were obtained when a speed of 1600 r.p.m.. was employed. Graphite is preferable to carbon as an anode material owing to itB greater density. Its liability to absorb gases Is considerably reduced. The oathode MMNB should be completely immersed in the eleotrolyte. This prevents the drawing in of air over the depositing surface, whioh would have a strong tendenoy to oxidize the depositing iron. No coating of the oathode is necessary. It should be polished very smooth and thoroughly cleaned. A slight piokling in acid before the run enables the deposit to be removed with greater ease. It was now decided to carry out a number of experiments using an iron anode (soluble) and to determine the connection, if any, (59). of the conditions for deposition from ferrous ohloride between the insoluble (graphite & oarbon) and soluble anode. These experiments constitute series C Eleven tests in all were oarried out, each of one hour duration, and with varying concentrations ef electrolyte and ourrent density. The temperatui'es were from 6*0° to 6*5°C and the speed was the same in each oase, 1600 r.p.m*. No diaphragm was used and the volume of the electrolyte was one litre. The anode consisted of a cylindrical pieoe of sheet iron. SERIES C Test. Current Density E.M.F. Temp.. Cone* of. Nature of Deposit. amps./sq.ft. volts. °C electrolyte. Qms.Fe/litre. 1. 121.0 1.0 81° 37.5 Dense crystalline: satin like surface: white: good. 2. 151.5 1.25 6*3° 37.5 Pitted: treed at bottom: fair. o 3. 151.5 1.25 82 50.0 No pits: finely orystalline: hard and brittle: silver white: very good. 4. 152.0 1.11 86° 80.0 Coarsely crystalline: brittle: no treeing: white: very good.. 5. 121.0 0.95 6*0° 100.0 Pitted: Soft and powdery: nobby at bottom: gray: poor. 6. 197.0 1.16* 85° 109.0 Coarsely orystalline: hard & brittle: white in colour: very good. 7. 91.0 0.50 6*1° 153.0 Finely orystalline: white: very good. 6*. 161.7 1.16 6*3° 155.0 Finely crystalline: white: small number of tiny knobs on surface: good. 9. 16*4.5 1.15 6*5° 151.0 Finely crystalline: white: good. (60). ( Series 0 continued.) Test. Current Density. E.M.F. Temp. Cone of Nature of Deposit. amps./sq.ft. volts. °C eleotrolyte. __ Gms. Fe/' 1i tr e. u 10. 197.0 1.33 85° 153.0 Nodular at bottom: few small pin holes: fair. 11. 212.0 1.25 55° 153.0 Rough and porous: powdery: very poor. A small amount of hydrated oxide of iron formed In the eleotrolyte during these runs. This seemed to have a beneficial effect on the nature of the deposits. It was mentioned in the preoeeding pages that at Grenoble, France, the electrolyte was thick with oxide sludge, which served as a mechanical polisher of the deposit, a depolarizer and neutrallzer ef the solution, (see p.6). The results of these experiments show that there is a limit to the current density whioh may be employed. In test No.l a current density of 121 amps, per sq.ft. gives a good deposit. But on increasing the ourrent density to 151*5 amps, per sq.ft. in the next test, the deposit is net so good. Tests Nos. 7 to 11 show this effect very olearly. By increasing the ourrent density from 91 to 212 amps, per sq.ft. in. solutions of the same oonoentration of ferrous ohloride, it is found that the deposits begin tt get poor as the current density reaches the higher figures. In tests Nos. 1, 8 & 9 the deposits are very good, but in No. 10 it is only fair and in No. 11 the deposit is very poor. The voltage necessary for the soluble anode eell is much lower than that required for the diaphragm oell. There is no formation of ferrio ciloride when an iron anode is used. The best conditions for deposition in a oell of this kind may be given generally as follows:*- (61). The temperature of the electrolyte should be between 50° and 90°C The current density should not exceed 150 amps, per sq.ft. and the concentration of the electrolyte should be about 150 grams of ferrous iron per litre. ( 540 gms. FeCl2 per litre.) The conditions are found to be practically the same for deposition as in the diaphragm oell and the insoluble anode. These deductions are very general in oharaoter, but no time was available to oontinue further with these experiments. Several speeimene were polished and examined under the microsoope. They showed the typical structure of pure iron (ferrite). A micro-photograph of a specimen from deposit 5 C is shown below. Specimen annealed at 900°0. for 5 min. Etched with 2% HNO5 in aloohol. Photographed under high power magnifloation, giving about 500 diameters. Shows fine crystalline struoture and polyhedral crystals of ferrite. There is no porosity or inclusions. (62). GENERAL CONCLUSION AND SUMMARY. The objeot of this thesis was set forth as an investigation into the problems connected with the leaching of pyrrhotite ores with ferrio ohloride and the production of iron by electrolysis of the resultant- ferrous ohloride solution. The results of the research have shown that pyrrhotite oan be successfully leaohed with ferrio ohloride solution. There are numerous conditions and limitations involved in the successful carrying out of this operation. The size of the ore particles, the temperature of the solution and the coacentration of the ferrio chloride leach are fundemental factors in the reaction. The leaching must be oarried out with agitation and air excluded as muoh as possible. Owing to the hydrolytic tendencies of ferric chloride in aqueous solution, the reaction must take plaoe at temperatures under 100°C The by-produots of the reaction, sulphur and copper,, constitute an important phase of the operation. Their reoovery and separation was not seriously attempted in this research. The sulphur la a direct result of the reaction, while the oopper depends on its preaenoe in the ore. The oopper le recovered from the ferrous ohloride solution; the sulphur is recovered from the residue of the leaoh. A summary of the results obtained and deductions arrived at are as follows:- 1. The maximum of iron extraoted from the ore was 96 %. 2. The solutions are totally reduoed from ferrio to ferrous chloride. 3* The sulphur is precipitated and remains in the residue* 4. Copper is. also aoted upon by the ferrio chloride* 5. The agitation should be sufficient to keep the ore from settling on the bottom of the container. (63). 6., The optimum temperature for extraotion is 95° 0. and this should not be exceeded. 7. Visible hydrolysis does not take plaoe at temperatures up to 95°C, provided the oonoentration of ferrio chloride is high. 8. The addition of acid to the leaching solution does not aid in extraction of iron unless over 10 % is added. 9. The ore should be ground to pass a 200 mesh screen. extraction 10. The time of maximum is from five to eight hours. 11. The concentration of the leaohing solution should be from 250 to 350 grams of ferrio chloride per litre in order to have a solution of high iron concentration Cor eleotrolysis. The electrolysis presented numerous problems and difficulties, and the results obtained have in moat oases been rather of a negative than a positive nature. The diaphragm oell and the use of insoluble anodes constitutes a muoh mere difficult problem than the ordinary deposition of iron from a cell oontaining an iron anode. In. brief the difficulty was to obtain a fine grained metallio deposit of iron. Even the best deposits were seen under the mieroscope to be porous. From the ordinary refining oell good deposits were obtained, fine grained and non porous. A general summary of the electro-deposition experiments is given as follows:- 1. The oathode compartment should be kept entirely free from ferrio ohloride. 2. The temperature of the electrolyte should be from 50° to 90°C. 3. The speed of the oathode should be high. 4. The concentration of the electrolyte should be from 150 to 150 gms. ferrous iron per litre. 5* The oathode should be smooth and highly polished- But a (64). Kind ooating of any le not neoessary. The deposit was in nearly all oases A easily removed. 6. Annealing of the deposited iron produces a very malleable and ductile metal. While the deposition of iron has not been as satisfaotory as one could wish, nevertheless with further research the difficulties that have been encountered could undoubtedly be overcome. The prooess as a whole is one that has very great possibilities. It reoovers a very pure grade of Iron from a hitherto almost useless ore. It produces this iron directly in a marketable f;orm without smelting. It reoovers as by-produots the sulphur and any oopper that may be present in the ore. It operates in a oyole, thus constituting an efficient plant operation. In Canada, where eleotrioal energy is abundant and the deposits of iron sulphide ore large, the near future should see the developement of this prooess and with it a further advance in the field of eleotro-ohemioal metallurgy. I am greatly indebted to the following gentlemen for their advice and assistance in the carrying out of this research:- Dr. Alfred Stansfield, under whose direction and supervision the work was oarried out. Dr. Otto Maasa. Mr. Harold J. Roast, F.C.S., F.C.I.C Mr. F.A.Eustis. Mr. W.. N. Crafts. Mr. Smith. I am also indebted to the Consolidated Mining and Smelting Co. Ltd., Trail, B.C. for a detailed sunimary of their work on producing Iron by the Eustis Prooess. (65). PART IV. APPENDIX. References. 1. FULTON. Principles of Metallurgy. p.13. 2. STOUGHTON. The Metallurgy of Iron and Steel. p.50. 5*. STANSFIELD. The Electric Furnace. pp. 197-211. 4..- COWPER-COLSS. Jnl. Iron and Steel Inst. No.Ill, 1905. — p. 154. 5. GUILLET. Jnl. Iron and Steel Inst. No.II, 1914. p.66. 6. COWPER-COLES. Same as reference No.4. 7. GUILLET. Same as reference No. 5* 5. BURGESS and HAMBUECHEN. Trans. Am. Eleotroch. Soo. 1904, Vol.5* p.201. 9. GUILLET. Same as reference No. 5« 10. COWPER-COLES. Same as reference No. 4. 11. ORAFTS. Information from Company "le FER#, Grenoble, France. 12. GUILLET. Same as referenoe No. 5. 13* GUILLET. Same as referenoe No. 5. 14. STOUGHTON. Chem. and Met. Eng. Vol. 26, No.3. Jan.15.1922.— p.125.. 15. EUSTIS. PROCESS DESCRIBED. Min. and Met. Deo. 1921. — p.17 Iron Age. Jan. 5* 1922. 16. BUTLER. Handbook of Mineralogy. p.35. 17. HANNEY. Report from Consolidated Min. and Smelting Co. Ltd., Trail,B.C. 15. HUGHES. Electro-deposition of Iron. Bulletin No.6. Dept. of Solentific and Industrial Research. Great Britain. 19. GUILLET. Same as referenoe No. 5. 20. GUILLET. * * • 21. STOUGHTON. Chem. and Met. Eng. Vol.26, No.3, 1922. p.125. 22. HUGHES. Electro-deposition of Iron. Bulletin No.6. 25. ALLMAND. Principles of Applied Eleotroohemistry. p.299. (66). 24. SMITH. General Chemistry for Colleges. p.500. 25. OSTWALD. Principles of Inorganic Chemistry. p.604. 26. •. Electrolytic Iron from Sulphide Ores. Chem. and Met. Eng. Vol.27,No.l4, Oct. 4.1922.——p.654. 27. GREENAWALT. The Hydr©metallurgy of Copper. p.215 & 220. 25. HANNEY. Same as referenoe No. 17. 29. ALLMAND. Prinoiples of Applied Electrochemistry. p.531. 30. LEHFELDT. Electro-Chemistro. Part I. — p.159. 31. MAASS. Personal referenoe. 32. KN0BEL,CAPLAN and EISEMAN. The Effeot of Current Density on Over voltage. Trans. Am. Slcotroeh. Soo. 1923. 53. See Referenoe No. 32. 34. NERNST. Theoretical Chemistry. 35* HUGHES. Electro-deposition of Ilron. Bulletin No.6. 36. HARKER. Petrology For Students. p.22* 37. SAUVEUR. The Metallography and Heat Treatment of Iron & Steel. —p.55. 35. FREUNDLICH and FISCHER. Zeit* f. Elektrooh. 1912. Vol.15. — p.556. 39. MAASS. Personal reference. 40. WYATT. Report of Memphremagog Copper Mine. June 5. 1559. 41. Report from Messrs. Lymans, Ltd. Montreal. (67). Sample Calculations. Standardizing of Ferrio Chloride Solutions for Leaching. 5 c.c. sample reduced with granulated zinc and analysed for iron by KMnOi} method. Fe in l.oo. .0506 gms. Clj in 1 oc. .0506 x 1.90 • .0961 gms. FeClj in 1 00. .0961 * .0506- .146T gms. Concentration of FeCl, per litre 146.7 grams. To Determine Amount of Standard Ferrio Chloride Solution Required for a Given Concentration. Ratio of ore to FcCl-5 1:?.97 (See page 25). Leach to be of following conoentratton:- 20 gms. of ore 59.4 gms. FeCl^/litre. Now there is 146.7 gms. of FeCl* in 1000 0.0. 1000 _ 1.0 gnu - * TTToT7 " 6.5 o.o. Amount of Stan. Solution required =» 59.4x6.5 = 403.9 o.o. To make up to volume of 1 litre add 596.1 c.c. of water. This gives solution of oono. of FeCl* of 59.4 gms./litre as required. For volume of 500 c.c. the values found above are halved. Calculations for Amount of Sulphur Precipitated in Reaction. 2FeCl3 * FeS '=* 3FeCl2 * S 56*32 32 For every 56 lbs. of iron dissolved 32 lbs. of. sulphur are precipitated. " " ton " " * 56 (65). Sample Calculation of Results of Leaohing Test. Test No.3 — Series J. CHARGE: 45 gms. ore 500 oc. FeCl3 sol. Cone. 267 gms./litre. Fe in ore — 23.02 gms. Fe in sol. 45.95 Agitation 5 hours. Ferrous Fe in sol.after run — 67.19 gms. 67 1 . .T. ,9 x 100 «, Per cent reduction 67.69 "" 99.2% Total Fe In sol. after run 67.69 gms. Initial Fe In sol. 45.95 &ns* 21.74 Inorease of iron 21.74 gms. Iron in ore 23.02 gms. -£iiZS x 100 ^ Per oent extraction 23.02 ~" 94.4$ (69). BIBLIOGRAPHY. CF.Burgess and CHambueohen. "Electrolytic Iron*1' Trans. Am. Eleotrooh. Soo.,1904,Vol.5,p.201 ; Eleotro-chem. Ind.Vol.2,p.l54,, W.M.Hicks and L.T. O'Shea. "'Some Points Connected with the Preparation of Pure Iron by Electrolysis". The Eleotrioian,1595, Vol. 35,p.543. E*Merok. D.R.P.* No. 126539, 1900. J.Eseard. Le Genie Civil,1919,vol.75, Nos.5,9&10. pp.165,199 & 225. A.tfatt. "Electrolysis of Iron Salts? The Electrician, 1557. Nov.ll&25. E.F.Kern. "Electrolytic Refining of Iron." Trans. Am. Eleotrooh. Soo. 1905,vol.13,p.103. S.Cowper-Coles."The Production of Finished Iron Sheets and Tubes in One Operation." Jnl. Iron & Steel Inst. 1905, No.3, p.134. CF.Burgess. "Eleotrolytlo Refining as a Step in the Production of Steel." Trans.Am.Eleotrooh.Soc.,1911,vol.19,p.151* W.E.Hughes. "The Eleotro-deposition of Iron." Bulletin No.6. Dept. of Scientific & Industrial Research, Gt. Britain. D.R.Kellogg. "Electrolytic Deposition of Iron for Building up Worn or Undersized Parts. Trans. Am.Inst.Min.&Met. 1922. Bradley Stoughton. "Eleotrolytlo Iron a Commercial Product." Chem. & Met. Eng. Vol. 26, No.3, p.125. F.H.Mason. "Iron from Pyrrhotite". Candn. Min. Jnl., Oct. 20.1922. A. Estelle. Estelle Prooess. Candn. Min. Jnl. Oct. 6.1922. A.J.Moxham. Prooess of treating ore to produce pure iron. U.S.Patents 1420127, 1420125, 1420129, 1420130. Patents. Eleotrolysls of Iron Ore.-- Can. Patent No. ?17243, Art of Making Electrolytic Iron.-- U.S.Patents 1432543,1412174. C.P.Perin and D.Beloher."Commeroial Production of Eleotrolytlo Iron" Min. & Met. Deo.1921, p.17*